Saekil Yun^a, Seung-Jun Lee^b, Sib Sankar Giri^a, Hyoun Joong Kim^a, Sang Geun Kim^a, Sang Wha Kim^a, Se Jin Han^a, Jun Kwon^a, Woo Taek Oh^a, Se Chang Park^a,*

^a Laboratory of Aquatic Biomedicine, College of Veterinary Medicine and Research Institute for Veterinary Science, Seoul National University, Seoul, 08826, Republic of Korea
^b Department of Pharmaceutical Science and Engineering, School of Convergence Bioscience and Technology, Seowon University, Cheongju, 28674, Republic of Korea

^*Corresponding author : Se Chang Park

Abstract
The aim of this study was to develop and evaluate a novel route of administration for vaccinating fish against Aeromonas hydrophila infection using a dissolving microneedles (MNs) patch. The A. hydrophila JUNAH strain was inactivated with formalin and used as a vaccine antigen. It was mixed with dissolvable carboxymethyl cellulose (CMC) as the matrix material to produce the MNs patches. When examined with a scanning electron microscope, each patch has 282 uniformly distributed, pyramid-shaped needles on a circular base. In the skin insertion experiment, the MNs patches were confirmed to be capable of penetrating the skin of the fish. Through agglutination assay and analysis of non-specific parameters like lysozyme and superoxide dismutase, it was verified that the antigen embedded into the patch induced adaptive and innate immune responses in the fish. In the challenge experiment, the group inoculated with the MNs patch and the group injected with formalin killed cells (FKC) showed a similar survival rate. Our results suggest that the FKC-loaded MNs patch is a wholly viable method alternative to injection for the vaccination of fish.

Keywords : Aeromonas hydrophila; Carboxymethyl cellulose; Cyprinid loach; Dissolving microneedles; Transcutaneous immunization